A method for rapid adjustment of hot-wire overheat ratio based on decimal resistance

Abstract

This invention discloses a rapid adjustment method for the overheat ratio of a hot wire based on decimal resistance, applied to the adjustment of the overheat ratio of a constant-temperature hot wire anemometer. The rapid adjustment method for the overheat ratio of a hot wire disclosed in this invention includes: a decimal resistance array (0) design, consisting of multiple rows of resistors, the output resistance of which is adjustable from 0Ω to 10000Ω and the minimum adjustment step is 0.1Ω; a switch-relay module (1), wherein each resistor array has a set of switches to control the relays to switch the resistance of the decimal resistance array (0); a switch control code (2), which encodes the switch control terminal of the switch-relay module (1), with one output resistor of the decimal resistance array (0) corresponding to a set of switch control codes; and a controller module (3), which calculates the corresponding switch control code (2) of the decimal resistance array (0) according to the required resistance value, and directly controls the switch-relay module (1) through the GPIO port to achieve switching of different resistances. This invention provides a rapid adjustment method for the overheat ratio of a constant-temperature hot-wire anemometer. In the Wheatstone bridge circuit, the output resistance of the decimal resistor array (0) is used as the overheat ratio adjustment resistor. The controller module (3) controls the switch-relay module (1) via GPIO port according to the switch control code (2) corresponding to the output resistance of the decimal resistor array (0) to achieve continuous step adjustment of the overheat ratio. The output resistance of the decimal resistor array (0) has a large adjustable range, high accuracy, wide frequency response, and short switching time. It also provides multiple adjustment steps, fully meeting the adjustment needs of different types of hot-wire overheat ratios currently on the market.

Description

Technical Field

[0001] This invention belongs to the field of flow field testing technology, specifically relating to a method for rapid adjustment of hot wire overheat ratio based on decimal resistance. Background Technology

[0002] In the field of flow field testing, isothermal hot-wire anemometers have significant advantages in terms of time resolution, dynamic frequency response, measurement repeatability, and continuous quantitative measurement of fluids. However, in compressible flow fields, the output voltage of isothermal hot-wire anemometers is affected by the combined effects of gas velocity, density, total temperature, and pressure. The variable hot-wire superheat ratio method can be used to solve for flow field pulsation parameters. This method requires that the flow field conditions remain stable during the continuous adjustment of multiple hot-wire superheat ratios; therefore, the adjustment of multiple hot-wire superheat ratios needs to be completed in the shortest possible time.

[0003] Currently, general-purpose constant-temperature hot-wire anemometers lack the capability to continuously change multiple hot-wire superheat ratios. Each change requires a complete and independent parameter setting and data acquisition process for the anemometer, resulting in a lengthy measurement time for a set of hot-wire superheat ratios. This makes maintaining the stability of compressible flow field conditions very difficult, or even infeasible. Therefore, there is an urgent need to solve the problem of rapidly adjusting the hot-wire superheat ratio in order to enable constant-temperature hot-wire anemometers to play a greater role in compressible flow field measurements. Summary of the Invention

[0004] The technical problem to be solved by this invention is to provide a method for rapid adjustment of the hot wire overheat ratio based on decimal resistance, which aims to solve the technical problem of continuous, automatic and rapid adjustment of the hot wire overheat ratio in constant temperature hot wire anemometers, and greatly improve the measurement efficiency based on the variable hot wire overheat ratio method.

[0005] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0006] The present invention provides a method for designing a hot wire overheat ratio fast adjustment circuit based on decimal resistance, comprising the following steps:

[0007] Step 1: Set up a decimal resistor array (0), which includes multiple resistor columns. Select high-precision, low-temperature-drift resistors. Arrange each resistor column in decimal order and output the resistance adjustment range and adjustment step size of the corresponding base position. For example, the resistance adjustment range of the resistor column output is 0Ω~0.9Ω, which corresponds to an adjustment step size of 0.1Ω. 0Ω~9Ω corresponds to an adjustment step size of 1Ω, and so on.

[0008] Step 2: Set up the switch-relay module (1), which consists of a switch and a relay group, to control the switching of the resistors in the decimal resistor array (0);

[0009] Step 3: Set the switch control code (2), encode the switch control terminal in the switch-relay module (1), and one output resistor of the decimal resistor array (0) corresponds to a set of switch control codes (2);

[0010] Step 4: Design a controller module (3) with a microcontroller, ARM processor, DSP and FPGA as the core, but not limited to microcontroller, ARM processor, DSP and FPGA. Use switch control code (2) to control the switch in the switch-relay module (1) through GPIO port, and then control the relay to switch the output resistance of the decimal resistor array (0) to the specified resistance value.

[0011] Step 5: Use the output resistor of the decimal resistor array (0) as the adjustable resistor R for the overheat ratio of the hot wire in the Wheatstone bridge of the constant temperature hot wire anemometer. b (33) A hot wire overheating ratio corresponds to a decimal resistor array (0), an output resistor, and a set of switch control codes (2). The controller module (3) controls the switch in the switch-relay module (1) through the GPIO port according to the switch control code (2) corresponding to the hot wire overheating ratio, thereby controlling the relay to switch the output resistor of the decimal resistor array (0) to the specified hot wire overheating ratio adjustment resistor value, so as to realize the rapid adjustment of the hot wire overheating ratio.

[0012] In step 5, the specific steps for rapidly adjusting the overheating ratio of the hot wire in a constant-temperature hot-wire anemometer based on the output resistance of the decimal resistor array (0) are as follows:

[0013] Step S1: Set the output resistor R of the decimal resistor array (0) to... b-1 End (00) and R b-2 Terminal (01) is connected to the Wheatstone bridge hot wire overheat ratio adjustable resistor R. b The position of (33);

[0014] Step S2: Set the hot wire overheat ratio 'a'. The hot wire overheat ratio is defined as follows: R f R is the cold resistance of the hot wire. w (34) is the working resistance of the hot wire;

[0015] Step S3: Calculate the operating resistance R of the hot wire w =(1+a)R f ;

[0016] Step S4: Calculate the overheating ratio adjustment resistor R in the Wheatstone bridge circuit. b (33) Resistance value R1(31) and R2(32) are the Wheatstone bridge arm resistors, R c(35) is the additional resistance (which is the sum of the resistance of the hot wire probe lead wire, the resistance of the hot wire probe support rod, and the resistance of the hot wire probe connecting cable);

[0017] Step S5: Set the output resistor of the decimal resistor array (0) to the hot wire overheat ratio adjustment resistor R. b (33) Resistance value, according to claim 4, the corresponding switch control code (2) is obtained, an overheat ratio corresponds to a decimal resistor array (0), an output resistor and a set of switch control codes (2);

[0018] Step S6: Repeat steps S2 to S5 to set one or more hot wire overheat ratios to obtain one or more sets of switch control codes (2) Code;

[0019] Step S7: Set the superheat ratio switching interval t: t = 0 for one superheat ratio, and t ≠ 0 for multiple superheat ratios;

[0020] Step S8: The controller module (3) controls the switches in the switch-relay module (1) sequentially through the GPIO port according to the set overheat ratio switching interval t, based on one or more sets of switch control codes (2), and sequentially sets the output resistor of the decimal resistor array (0) to different hot wire overheat ratio adjustment resistors R. b (33) Resistance value, thereby realizing continuous, automatic and rapid adjustment of the hot wire overheating ratio.

[0021] The advantages of this invention are as follows: This invention provides a rapid adjustment method for the hot-wire superheat ratio based on a decimal resistor, used for adjusting the hot-wire superheat ratio of a constant-temperature hot-wire anemometer. This decimal resistor has a wide adjustable range, high accuracy, and wide frequency response, while providing multiple adjustment steps, fully meeting the adjustment needs of different types of hot-wire superheat ratios currently on the market. The decimal resistor has a short switching time, reaching 1ms, enabling rapid adjustment of the hot-wire superheat ratio. Therefore, using this decimal resistor, continuous, automatic, and rapid adjustment of the hot-wire superheat ratio of a constant-temperature hot-wire anemometer can be achieved, solving the difficult problems of long adjustment times and unstable flow fields over large time spans in variable hot-wire superheat ratio methods, greatly improving measurement efficiency and accuracy. Attached Figure Description

[0022] Figure 1 This is a structural design block diagram of the present invention;

[0023] Figure 2 This is a schematic diagram of the design of the decimal resistor array and its switch-relay module of the present invention.

[0024] Figure 3 This is a schematic diagram illustrating the application principle of the decimal resistor in the adjustment of the overheat ratio of the hot wire in a constant-temperature hot-wire anemometer.

[0025] Figure 4 The present invention relates to the experimental results of using the decimal resistor of the present invention for continuous adjustment of the overheat ratio of five hot wires in a constant temperature hot wire anemometer. Detailed Implementation

[0026] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments. The described embodiments are only some embodiments of the present invention. Based on the present invention, all other embodiments obtained by researchers or those skilled in the art without creative work are within the scope of protection of the present invention.

[0027] Example 1

[0028] The hot-wire overheat ratio fast adjustment circuit design based on decimal resistor in this embodiment has been effectively verified through experiments on the hot-wire overheat ratio adjustment of a constant-temperature hot-wire anemometer.

[0029] The specific implementation steps of this invention are as follows:

[0030] Step 1: Set up a decimal resistor array (0), which includes multiple resistor columns. Select high-precision, low-temperature-drift resistors. Arrange each resistor column in decimal order and output the resistance adjustment range and adjustment step size of the corresponding base position. For example, the resistance adjustment range of the resistor column output is 0Ω~0.9Ω, which corresponds to an adjustment step size of 0.1Ω. 0Ω~9Ω corresponds to an adjustment step size of 1Ω, and so on.

[0031] Step 2: Design a switch-relay module (1), consisting of a switch and a relay group, to control the switching of the resistors in the decimal resistor array (0);

[0032] Step 3: Set the switch control code (2), encode the switch control terminal in the switch-relay module (1), and one output resistor of the decimal resistor array (0) corresponds to a set of switch control codes (2);

[0033] Step 4: Design a controller module (3) based on GD32, and use switch control code (2) to control the switch in the switch-relay module (1) through GPIO port, thereby controlling the relay to switch the output resistance of the decimal resistor array (0) to a specified resistance value.

[0034] Step 5: Use the output resistor of the decimal resistor array (0) as the adjustable resistor R for the overheat ratio of the hot wire in the Wheatstone bridge of the constant temperature hot wire anemometer. b(33) A hot wire overheat ratio corresponds to a decimal resistor array (0), an output resistor, and a set of switch control codes (2). The GD32 controller module (3) controls the switch in the switch-relay module (1) through the GPIO port according to the switch control code (2) corresponding to the hot wire overheat ratio, thereby controlling the relay to switch the output resistor of the decimal resistor array (0) to the specified hot wire overheat ratio adjustment resistor value, thereby realizing the rapid adjustment of the hot wire overheat ratio.

[0035] In step 5, the cold-state resistance R of the hot wire in this embodiment... f The resistance is 5.54Ω, the Wheatstone bridge arm resistors R1 is 20Ω, R2 is 400Ω, and the additional resistor R... c The current is 0.56Ω; five hot wire superheat ratios a1 to a5 are changed, with a1 < a2 < a3 < a4 < a5; the flow field conditions remain stable during the measurement. The specific steps for rapid adjustment of the hot wire superheat ratio in a constant-temperature hot wire anemometer based on the output resistance of a decimal resistor array are as follows:

[0036] Step S1: The output resistor R of the decimal resistor array b-1 End and R b-2 The terminal is connected to the Wheatstone Bridge hot wire overheat ratio adjustable resistor R. b The position of (33);

[0037] Step S2: Set the hot wire overheat ratio a = a1;

[0038] Step S3: Calculate the operating resistance R of the hot wire w =R w1 =(1+a1)R f ;

[0039] Step S4: Calculate the overheating ratio adjustment resistor in the Wheatstone bridge circuit.

[0040] Step S5: Set the output resistance of the decimal resistor network to R. b1 According to step 4, the corresponding switch control code is obtained;

[0041] Step S6: Repeat steps S2 to S5, setting the hot wire overheat ratio to a2, a3, a4, and a5 respectively, with corresponding hot wire overheat ratio adjustment resistors R. b2 R b3 R b4 and R b5 Thus, multiple sets of corresponding decimal resistor array switch control codes are obtained;

[0042] Step S7: Set the superheat ratio switching interval time t = 10ms;

[0043] Step S8: Every 10ms, the GD32 controller module controls the switches in the switch-relay module sequentially via the GPIO port according to the switch control code sequence, and sequentially sets the output resistance of the decimal resistor array to R. b1 R b2 R b3 R b4 and R b5 This enables continuous, automatic, and rapid adjustment of the hot-wire overheat ratio. The experimental results of using a decimal resistor for continuous adjustment of the overheat ratio of five hot-wires in a constant-temperature hot-wire anemometer are as follows: Figure 4 As shown, Figure 4 The curves in segments ① to ⑤ represent the output voltages of the constant-temperature hot-wire anemometer when the superheat ratios are a1, a2, a3, a4, and a5, respectively. As the superheat ratio increases, the output voltage also gradually increases, thus realizing the flow field measurement of the constant-temperature hot-wire anemometer with continuously varying superheat ratios.

[0044] The flow field measurement of the variable hot wire superheat ratio using a hot wire superheat ratio method based on decimal resistance, as described in this invention, was performed on a constant-temperature hot wire anemometer. Previously, the measurement needed to be interrupted during the change of the hot wire superheat ratio. This invention enables continuous and automatic adjustment of the hot wire superheat ratio; and the adjustment time is as short as 1 millisecond, reducing the time required for measuring the variable hot wire superheat ratio from several minutes or tens of seconds to a few milliseconds, thus achieving rapid adjustment of the hot wire superheat ratio.

Claims

1. A method for rapid adjustment of the overheat ratio of a hot wire based on decimal resistance, characterized in that: The circuit consists of a decimal resistor array (0), a switch-relay module (1), a switch control code (2), and a controller module (3). In the Wheatstone bridge circuit of the constant-temperature hot-wire anemometer, the output resistance of the decimal resistor array (0) is used as the hot-wire overheat ratio adjustment resistor. The controller module (3) directly controls the switch in the switch-relay module (1) through the GPIO port according to the switch control terminal code (2) corresponding to the output resistance of the decimal resistor array (0), thereby controlling the relay to switch the output resistance of the decimal resistor array (0) to the specified hot-wire overheat ratio adjustment resistor value, thus realizing the rapid adjustment of the hot-wire overheat ratio.

2. The method for rapid adjustment of hot wire overheat ratio based on decimal resistors according to claim 1, wherein the specific steps of the decimal resistor array (0) include: To accommodate different resistance adjustment ranges with varying precision, multiple resistor columns are constructed, each consisting of several resistors with different resistance values. These resistor columns utilize high-precision, low-temperature-drift resistors, arranged in decimal order, and output the corresponding resistance adjustment range and adjustment step size in the decimal place value. For example, a resistance adjustment range of 0Ω to 0.9Ω corresponds to an adjustment step size of 0.1Ω, 0Ω to 9Ω corresponds to an adjustment step size of 1Ω, and so on.

3. The method for rapid adjustment of hot wire overheat ratio based on decimal resistance according to claim 1, the specific steps of the switching relay module (1) include: For different resistor arrays, a switch-relay module is designed to control the switching of resistors with different resistance values ​​to achieve different resistance value outputs.

4. According to the method for rapid adjustment of hot wire overheat ratio based on decimal resistor as described in claim 1, the specific steps of switch control encoding (2) are as follows: the switch control terminal in the switch-relay module is encoded to correspond to the output resistance of the decimal resistor array (0).

5. According to the method for rapid adjustment of hot wire overheat ratio based on decimal resistance as described in claim 1, the specific steps of the controller module (3) are as follows: design a controller module with a microcontroller, ARM processor, DSP and FPGA as the core, but not limited to microcontroller, ARM processor, DSP and FPGA, use switch control code (2) to control the switch in the switch-relay module (1) through GPIO port, and then control the relay to switch the output resistance of the decimal resistance array (0) to the specified resistance value.

6. The method for rapid adjustment of the overheat ratio of a hot wire based on decimal resistance according to claim 1, the rapid adjustment process of the overheat ratio of a constant-temperature hot wire anemometer includes the following steps: Step S1: Set the output resistor R of the decimal resistor array (0) to... b-1 End (00) and R b-2 Terminal (01) is connected to the Wheatstone bridge hot wire overheat ratio adjustable resistor R. b The position of (33); Step S2: Set the hot wire overheat ratio 'a'. The hot wire overheat ratio is defined as follows: R f R is the cold resistance of the hot wire. w (34) is the working resistance of the hot wire; Step S3: Calculate the operating resistance R of the hot wire w =(1+a)R f ; Step S4: Calculate the overheating ratio adjustment resistor R in the Wheatstone bridge circuit. b (33) Resistance value R1(31) and R2(32) are the Wheatstone bridge arm resistors, R c (35) is the additional resistance (which is the sum of the resistance of the hot wire probe lead wire, the resistance of the hot wire probe support rod, and the resistance of the hot wire probe connecting cable); Step S5: Set the output resistor of the decimal resistor array (0) to the hot wire overheat ratio adjustment resistor R. b (33) Resistance value. According to claim 4, the corresponding switch control code (2) is obtained, where an overheat ratio corresponds to a decimal resistor array (0), an output resistor, and a set of switch control codes (2); Step S6: Repeat steps S2 to S5 to set one or more hot wire overheat ratios to obtain one or more sets of switch control codes (2); Step S7: Set the superheat ratio switching interval t: t = 0 for one superheat ratio, and t ≠ 0 for multiple superheat ratios; Step S8: The controller module (3) controls the switches in the switch-relay module (1) sequentially through the GPIO port according to the set overheat ratio switching interval t, based on one or more sets of switch control codes (2), and sequentially sets the output resistor of the decimal resistor array (0) to different hot wire overheat ratio adjustment resistors R. b (33) Resistance value, thereby realizing continuous, automatic and rapid adjustment of the hot wire overheating ratio.

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